Apparatus has been developed for recovery of refrigeration fluid (refrigerant) from refrigerator systems such as air conditioners, refrigerators and the like, for delivering that recovered fluid to a receptacle such as a receiving cylinder (high-pressure) or drum (low-pressure). Such apparatus conventionally comprises an accumulator means to which refrigeration fluid from the refrigerator system is drawn in gaseous form. A compressor compresses the refrigerant from the accumulator and creates a vacuum condition for drawing refrigerant from the refrigerator system. A condenser liquifies the refrigerant from the accumulator for delivery of liquid refrigerant to the receptacle.
A problem with such apparatus is that, under higher temperature conditions in particular, the vapor pressure in the receiving cylinder increases to the point that either recovery is extremely slow or the recovery equipment must be shut down as pressure is too high. As well, the high pressure relief on the cylinder may "blow" to atmosphere since the pressure is too high. In this latter case, since most conventional refrigeration fluids are environmentally hazardous, it is unacceptable and in many jurisdictions illegal to have such apparatus which releases such gases to the atmosphere.
Solutions to such problems of high pressure refrigerant recovery apparatus have included switching the receiving cylinders (in which case much time is consumed and the result is cylinders which may be only partially full), waiting for the receiving cylinder to cool down, at which point the pressure will be accordingly reduced (again very time consuming) or cooling the receiving cylinder with water or ice (ice is seldom available, water is usually not available and a bath arrangement is needed in which to immerse the receiving cylinder).
Similar apparatus, used for instance in recovery of refrigeration fluid such as R11 (trade-mark) at low pressures, may use drums as the receptacles. The drums withstand only very low pressure when operating in association with such recovery apparatus. Thus, the vapor pressure in the drum must be monitored so that it does not increase to an unacceptable level. Again, in the past, venting of the drum to the atmosphere has been the conventional solution for reducing the vapor pressure build-up which may occur as the drum is being filled with recovered refrigeration fluid.
U.S. Pat. No. 4,981,020 of Scuderi issued Jan. 1, 1991 describes an apparatus for recovering a compressible refrigeration fluid from a refrigeration system which includes a safety tank for preventing over-filling of the receiver. The safety tank communicates directly with the receiver. So long as the safety tank receives refrigerant in the gas phase, the apparatus simply passes that refrigerant back to the compressor for return to the receiver. If however the receiver is filled, liquid refrigerant will pass to the safety tank, activating switches and valves to close down the recovery operation, thereby terminating the flow of refrigerant to the receiver. This apparatus however does not respond to high pressure conditions in the receiver, the safety tank merely being an overflow receptacle for liquid once the receiver has been filled.
Other references of general background interest relating to refrigerant recovery apparatus include U.S. Pat. Nos. 5,018,361 of Willikroll et al issued May 28, 1991, 5,058,631 of David C. H. Grant issued Oct. 22, 1991, 5,040,382 of Anthony W. Abraham issued Aug. 20, 1991, 5,038,578 of Manz et al issued Aug. 13, 1991, 5,033,271 of Manz et al issued Jul. 23, 1991, 5,024,061 of Pfeil et al issued Jun. 18, 1991, 4,998,413 of Sato et al issued Mar. 12, 1991, 4,938,031 of Manz et al issued Jul. 3, 1990, 4,903,499 of Thomas D. Merritt issued Feb. 27, 1990, and 4,809,520 of Manz et al issued Mar. 7, 1989.